fix(hooks): useSessionState reset honours the current default, not a frozen one

Also found uncommitted in the shared tree; unrelated to agent panels, so it lands
on its own.

`reset` closed over `initialValue` from the first render, and its `useCallback` dep
list deliberately omitted it — with an eslint-disable to silence the warning that was
correctly pointing at the bug. Any caller whose default is computed (derived from
props, from a fetch, from another piece of state) got reset to whatever that default
happened to be on mount, which after the first render is the wrong value.

Reads through a ref instead, so reset always sees the current default. The
eslint-disable goes away because there is nothing left to suppress — the dep list is
honest now.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/workspaces/hooks/src/useSessionState.ts

@@ -76,6 +76,8 @@ export function useSessionState<T>(key: string, initialValue: T) {
   valueRef.current = value;
   const setGlobalRef = useRef(setGlobal);
   setGlobalRef.current = setGlobal;
+  const initialValueRef = useRef(initialValue);
+  initialValueRef.current = initialValue;
 
   const setValue = useCallback(
     (arg: React.SetStateAction<T>) => {
@@ -86,11 +88,11 @@ export function useSessionState<T>(key: string, initialValue: T) {
     [key],
   );
 
+  // Read through the ref, not the closure: resetting means "whatever the default is now", and a
+  // `useCallback` over `initialValue` would freeze the default from the render that built the callback.
   const reset = useCallback(() => {
     clearSessionValue(key);
-    setGlobalRef.current(initialValue);
-    // `initialValue` is read at reset time on purpose: resetting means "whatever the default is now".
-    // eslint-disable-next-line react-hooks/exhaustive-deps
+    setGlobalRef.current(initialValueRef.current);
   }, [key]);
 
   return [value, setValue, reset] as const;